Process of obtaining ammonium salts from gas.



973,164. @gamma mi. ia? im.

UNITED STATES PATENT OFFICE.

PROCESS 0F OBTAINING AMMONIUM SALTS FROM GAS.

Specification o1' Letters Patent.

Patented Oct. 18, 1910.

Application tiled ctolier 7, 1908. Serial No. 456,668.

To all whom it may concern:

Be it known that I, KARL BURxnnrsnn, a subject of the German Emperor,residing at Aix-la-Chapelle, Germany, have invented new and usefulImprovements in Processes of Obtaining Ammonium Salts from Gas, of whichthe following is a specification.

This invention relates to a process of obtaining ammonium salts fromgases, such as illuminating gas or coke oven gas, in .a simple andeconomical manner- For this pur ose the sulfur and ammonia contained 1ne gas are caused to so interact as to directly produce ammonium suliteor ammonium sulfate.

1'n carrying out my process, the gas is passed oer a substancle Whicheraable of 'i 0o o en, suc as roa og iron ievniid sugtgance being heated toa teniperature at which condensation of the water contained in the gas,is prevented, said temperature being under normal conditions (iO-70 C.The oxidizing substance is either continuously r enerated by adding airor pure oxygen to t e s passing thereover, or it is intermittent yregenerated by passing alternately gas and air currents over saidsubstance. If the oxidizing substance is continuously regenerated andheated to the temperature of oxidizing sulfureted hydrogen, the latteris decomposed into sulurous acid and water, while at higherteinperatures and with a siiiicient supily of oxygen, sulfuric anhydridis forme If, however, the oxidizing substance is intermittentlyregenerated, there occurs firstan oxidation to sulfur compounds whichare subsequently higher oxidized when oxygen is passed oi-'er saidcompounds. The sulfur dioxid or sulfur trioxid reacts on the ammoniacontained in the gas with which it will form acid or neutral sulfite orsulfate of ammonia. The reactions takin place with a continuousregeneration of tie oxidizing substance yield, in the Erst case,'an acidsalt, while, in the second case, a neutral salt is obtained, owing tothe combination of twice the quantity of ammonia with the l samequantity of sulfurous acid, the reactions being as follows:

NH4/SO For illustrating the reactions that take place whenintermittently regenerating, it may be assumed that oxid of iron beused` as oxidizing agent. During the first step the sulfureted hydrogencombines therewith, while during the second step the oxidizing substanceis regenerated and the sulfur oxygen compound is formed according to thefollowing formula:

Owing to the contact between the sulfur oxygen compounds thus formed andthe ammonia, the above described reactions will either yield an acidsalt or a neutral salt according to the quantit)1 of ammonia present.

The accompanying drawin illustrates a diagrammatic elevation of a p antfor carrying` out my process.

he numeral 10 indicates a gas duct connected to thc ovens or tarseparators, (not shown), and opening into a chamber 1l which is heatedby. pipe coil 12. The lattcr communicates by pipe 13 with a suitablesteam supply, the steam being discharged from coil 12 through pipe 14.Chamber 1l is, by duct 15, connected with a suitable distilliii apaiatus 1G which is, at its top, supplie with) aniinoniacal liquordischarged from tank 17 through pipe 4S. Still 1G is, by pi 18,connected to a air of oxdizinlr being controlled by cocks 19, 20,respectively. Chambers Q1, 22 contain a suitable oxidizinrir substance.such as roasted bogiioii ore, an( are, by pipe 9.5, connected with asuitable washing apparatus 29, communication therewith being cont-rolledby cocks 23 and 24.

cliani rs 21, 22, communication therewith In like manner, chambers 21,22 communicate by pipe 28, controlled by cocks 26, 27, respectively,with a washing apparatus 30. Yashers 29, 30 are lnndc in the torni oftowers containing coke, twigs or similar in aterial, and are providedwith upper discharge pipes 31, 32 of winch pipe 31 1s connected to thegas mains (not shown) while pipe 32 opens into the atmosphere. Abovetowers 29, 30, are arranged tanks 33, 34, communication therewith beingcontrolled by cocks 35, 36, respectively. The liquor collecting at thebottom of towers 29, 30 1s, by pipes 37, 39 conveyed to basins 38, 40,respectively. Basin 38 is, b f pipe 42, connected to tank 33,a pum 41ing employed for raising the liquor m the basin into the tank. In likemanner, basin 40 is, by pipe 44, and pump 43, connected to tank 34. Anair pipe 45 opens into chambers 21, 22, communication therewith beingcontrolled by cocks 46, 47.

The rocess is as follows: The raw gas is prefera ly cooled to effect theseparation of tar. The aqueous condensate formed thereby contains alarge quantity of ammonia, said condensate being continuously conveyedinto tank 17, from which it Hows into the distilling aaratus 16. The rawgas which contains sul) reted hydrogen and that peortion of the ammoniawhich has not en precipitated during the cooling of the gas, entersheater 11 through pi 10, from when it is conveyed, through pipe 15, intodist-illing apparatus 16. In the latter the rising hot gas encountersthe descending gas water and takes up its ammonia. In order to separatethe ammonia, which has already been bound to acids, the distillingapparatus may contain lime or some other basic substance. During theprocess described, the gas current again takes up the ammoniaprecipitated with the gas water and is heated to such a degree as isnecessary for heating the lntidizing substance It may here be stated,that when adapting old plants to my improved process, in which plantsthe entire l quantity of ammonia is separated by Washing the gas, and inwhich, consequently, the gas Water contains all of the ammonia, the gasentering through i 10 carries only sulfureted hydrogen. gas leavin still16 is then conveyed to oxidizing clamber 22, cock 19 bein closed andcock 20 opened. In this cham er the sulfureted hydrogen is separated inthe forni of sulfur com ounds or sulfur iron compounds, while t e gascarrying the ammonia enters through open cock 24 into washing apparatus29. The temperature, .which should be maintained in chamber 22 by theintlowing gus, depends upon the amount of moisture carried thereby andshould be rcf ernbly between and 7()0 cent-ignite, so as to avoid theformation of condensatcs upon the bog iron ore.

Attention may be called to the fact, that the process may also becarried out at atmospheric temperature, but a temperature higher than120 centigradc should be avoided, because, in that case the sulfur meltsand thus is a t to be readily taken along by the gas. he tem raturewhich the oxidizing agent should ve cannot be lixed,as said temperaturechanges constantly according to the center of reaction, and asfurthermore, there occurs at this place a generation of heat owing tothe strong exothermic reaction.

While the process described is going on, valve 47 is closed, While valve46 is o ned, so that an air current, passing throng pipe 45, enterschamber 21. This current regenerates the oxidizing subst-ance andsimultaneously oxidizes the com ounds of sulfur or sulfur iron, therebyorming sulfurous acid. The air carryi the latter enters washingapparatus 30 an escapes through pipe 32 into the atmosphere, duringwhich process cock 27 is closed, while valve 26 is opened. In washingapparatus 30, which is rinsed with the liquor leaving tank 33, the

sulfurous acid is retained, the 1i uor formed flowing throuv'h pipe 39into basin 40. From the latter the liquor is, by pipe 44 and pum 43,conveyed to tank 34, to be discharge into washing apparatus 29. As thelatter is traversed by gas carrying ammonia, the washing of said gas isaccompanied by a combination of the ammonia contained in the gas withthe sulfurous acid contained in the washing liquor, thereby forming asalt. As said liquor is present in excess within tower 29, the salt thusformed is dissolved in the liquor and flows with the latter into basin38. From this basin the salt solution is, by pipe 42 and pump 41,returned to tank 33, so that it wlll again become saturated withsulfurous acid and so on.

The advantage of my improved process consists-in the fact that the gas,as well as the air, after leaving the oxidizing cham* ber, arealternately brought into contact with the same washing liquor, and thatthe latter brings about the reaction between the ammolna and the acidpreviously formed, without permitting the carriers of the ammonia andacid, z'. e., the gas and the air, to come into contact with oneanother. In this way the liquor eifectin the above reaction is graduallyenriche with thioammonium salts, until it is saturated therewith,thereby avoiding the presence of an excess of free acid or free ammonia.The slight excess of one substance at each stage of the process,however, renders the washin liquor well adapted for absorbing the ot ersubstance, as such liquor has a ater tendency than pure water for absoring the ammonia or siilfurous acid. The resulting salt collects at thebottom of basin 38 from which it may be removed from time to time.

After the oxidizing substance contained within chamber 22, has beenexhausted, all cocks are reversed, so that the gas will now ow throughchamber 2l into tower 29,while the air passes through chamber 22 intotower 30, thus permitting a continuation of the process withoutinterruption. H theamount of sulfiireted hydrogen is excessive, part ofthe air charged with acid, while passin the oxidizing chamber, may bebranched o before entering the washing tower. Thisse ara-ted aircarrying acid may either be 's charged into the atmosphere, or may beutilized for other purposes. For that part of the air which is thuswithdrawn, the oxidizing chamber acts merely as a purifier. If thereshould occur a deficiency of acid, suitable acids may be added to thewashing li uor.

n lieu of treating the precipitated gas water with the raw gas, theregenerating air maybe utilized for this purpose. In this case, air isadmitted through pipe 10, while the gas enters through pipe 45. When theair, that now constitutes the ammonia carrier, passes the oxidizingchamber, there occurs simultaneously with the regeneration of theoxidizing agent, the formation of thioaminonium salts owing to thepresence of acid. These salts, together with the excess of free acid.will be taken up by the washing liquor. It my process is to be carriedout in an old plant, in which all the ammonia is contained in thc gaswater, the air may be charged with the entire quantity of ammonia, sothat the raw gas constitutes a carrier for sulfureted hydrogen only.

Generally it will not be necessary to conducttlie entire quantity of airthrough the distilling apparatus 16, so that part thereof may bebranched oit after it has passed the heating chamber to be directlyconiveyed to pie 18..

claim:

1. Process of obtaining ammonium salts from gas containing sulfuretedhydrogen and ammonia, which consists iii converting the sulfuretedhydrogen into sulfur ox gen compounds by contact with an oxidizinglagent, causing said compounds to react with the ammonia contained in thegas, and regenerating tlie oxidizing agent by passing an air currentthereover.

2. Process of obtaining ammonium salts from gas containing sulfuretedhydrogen and ammonia, which consists in passing the gas over anoxidizing a ent to retain the 4sulfureted hydrogen in t e form of sulfurcompounds, regenerating the :went and converting the sulfur compoundsinto acid anhydrid by passing an air current over said agent, andseparately washing the gas carryin the ammonia and the air carrying theacid with the same liquid, to retain the ammonia and the acid anhydridand cause a reaction between these ases.

3. Process of obtainin ammonium salts from gas containing su furetedhydrogen and ammonia, which consists in passing the gas over anoxidizing agent in a lurality of alternately traversed contact chambers,to retain the sulfureted hydrogen in the form of sulfur compounds,passing a current of air through those chambers which were previouslytraversed by the gas, to regenerate the oxidizing agent and to convertthe sulfur compounds into acid anhydrid, washing the gas carrying theammonia and the air carrying the acid in diterent washers with the sameliquid to retain the ammonia and the sulurous acid and cause a. reactionbetween these gases, said washing liquid flowing in a continuous cyclethrough al the washers.

4. Process of obtaining ammonium salts from gas containing sulfuretedhydrogen and ammonia, which consists in cooling said mixture torecipitate ammoniaca] liquor, heating said iquor in the presence of acurrent of air adapted to absorb the ammonia therefrom, converting thesulfiireted hydrogen of the residual gas into acid anliydrid by contactwith an oxidizing agent, whereby the siilureted hydrogen is retained inthe forni of sulfur compounds, passing the air carrying the ammonia oversaid agent to regenerate the saine and to convert the sulfur compoundsinto acid anhydrid, separately washing the gas carrying the ammonia andthe air carrying the acid with the same liquid to retain the ammonia andthe sulfurons acid and cause a reaction between these gases.

In witne whereof I have signed this specification in the presence of twowitnesses.

KARL BURKHEISER.

.vi/ritnesses:

HENRY QUADFLIEG, Winnaar J. REUTERS.

